Optical weft stop motion for a weaving machine

ABSTRACT

Upon occurrence of a weft yarn break the photocell is fully illuminated so that the Schmitt trigger is activated to change the state of the monostable multivibrator which thus deactivates the weaving machine. Further, in the absence of a weft yarn in the light path after picking, should the illumination of the photocell fall below a predetermined value, the voltage of the Schmitt trigger and a time network voltage are used to deactivate the weaving machine.

United States Patent lnventor Karl llohener St. Gall, Switzerland Appl.No. 864,690 Filed Oct. 8, 1969 Patented Sept. 28, 1971 Assignee SulzerBrothers, Ltd.

Winterthur, Switzerland Priority Oct. 10, 1968 Switzerland 15134/68OPTICAL WEF'I STOP MOTION FOR A WEAVING MACHINE 5 Claims, 2 DrawingFigs.

US. Cl. 139/370, 139/273, 139/336 Int. Cl. ..D03d 51/18, D03d 51/34,GOln 21/30 Field of Search 139/273,

[56] References Cited UNITED STATES PATENTS 3,139,911 7/1964 Breitmeier139/370 3,379,225 4/1968 lchimi et a]. 139/353 3,440,634 4/1969 Maurmannet al.. 139/370 3,489,910 1/1970 Bohme et a1 139/370 PrimaryExaminer-Henry S. Jaudon Attorney-Kenyon & Kenyon Reilly Carr & ChapinABSTRACT: Upon occurrence of a weft yam break the photocell is fullyilluminated so that the Schmitt trigger is activated to change the stateof the monostable multivibrator which thus deactivates the weavingmachine. Further, in the absence of a weft yarn in the light path afterpicking, should the illumination of the photocell fall below apredetermined value, the voltage of the Schmitt trigger and a timenetwork voltage are used to deactivate the weaving machine.

30a 30 30c 32 32c OPTICAL WEFT STOP MOTION FOR A WEAVING MACHINE Thisinvention relates to an optical weft stop motion for a weaving machine.

Heretofore, it has been known to use optical means in order to detectthe presence or absence of weft yarns in weaving machines. Generally,such means included a transmitter for emitting a beam of lighttransversely in the direction of the weft yarn towards a photoelectriccell situated behind the weft. in the event that a weft yarn waspresent, the beam was interrupted by the weft yarn so that the beam didnot reach the photoelectric cell. Thus, the cell did not initiate anyswitching operations to stop the weaving machine.

However, experience has shown that'the soiling of an optical weft yarnstop motion is a serious problem. For example, dust and fluff can settleon the optical parts, i.e. the lenses and the photosensitive element ofthe transmitter and receiver, such as to interfere with the beam oflight. Also, lubricating oil adhering to the shuttle can settle in theform of a mist in mixture with dust on the optical parts. Experience hasfurther shown that the intensity of the beam should have a relativelylow value, and this is of course adjusted when the optical parts areclean. Consequently, when the transmitter and/or the receiver becomedirty, the beam intensity operative in the receiver is so reduced thatthe receiver reacts as if a weft yarn had been introduced even if suchis not the case. When fibrous yarns are being used, some of the fibersfrequently work loose when the weft is inserted and may pass into thebeam of the weft yarn stop motion and then also simulate the presence ofa weft yarn. The monitoring of the weft yarn insertion by the weft yarnstop motion is thus no longer reliable and the weaving machine maytherefore produce faulty fabric which goes unnoticed.

Accordingly, it is an object of the invention to reliably monitor theinsertion of weft yarns without being obstructed by the inevitablefluff, oil mist and fibers.

It is another objection of the invention to be able to automaticallyswitch off a weaving machine when the optical parts of an optical stopmotion become excessively soiled.

Briefly, the invention provides an optical weft stop motion for aweaving machine which is not only capable of monitoring the presence ofabsence of a weft yarn during a picking operation in order to deactivatethe weaving machine in the event of the absence of the weft yarn butalso capable of determining the degree of soiling of the optical partsof the stop motion after a picking operation in order to deactivate theweaving machine in the event of excessive soiling. The optical weft stopmotion can also determine the presence of a tangled yarn after a pickingoperation has been completed.

The optical weft stop motion includes a transmitter for emitting a beamof light in the direction of the path of a weft yarn and a receiver forreceiving the beam. The receiver includes a switching means which causesthe weaving machine to stop if no weft yarn is introduced. The switchingmeans also initiates switching operations if the intensity of the beamacting on the receiver drops below a specified value. The advantage isthat as soon as the optical parts have become so dirty that the weftyarn stop motion no longer operates reliably the weaving machine isstopped.

These and other objects of the invention will become more apparent fromthe following detailed description and the accompanied drawings inwhich:

FIG. 1 illustrates a general view of a weaving machine from the fabricend; and

FIG. 2 illustrates a circuit diagram of a weft yarn stop motionaccording to the invention.

Referring to FIG. 1, the weaving machine is constructed with two sideplates 1, 2 between which are disposed a warp beam (not shown) a clothbeam 3, a guide and tensioning means (not shown) for the warp andfabric, a central member 4 connecting the two side plates 1, 2, and amain drive shaft 5 for the machine. In addition, a heddle shaft 6forming part of a shedding mechanism and a reed 7 are mounted betweenthe side plates 1, 2 as is known.

A picking mechanism 8 which projects a shuttle is mounted on the plate 1while a catching mechanism 9 is disposed on the right-hand side of themachine as shown to receive the shuttle at the end of a picking (orinserting) operation. A weft yarn 10 is drawn from a feed bobbin 11,which is usually fixed outside the shed, through a screen 12 and avertically movable yam tensioning. device 13 and introduced into theshed as is known.

After insertion of the weft yarn, the shuttle is pushed back slightly inthe catching mechanism 9 so that it has exactly the same position oneach pick. The yarn tensioning device 13 is moved into the top positionin these conditions, so that the weft yarn always remains tensioned onthe reverse movement of the shuttle. During the pushing back movement ofthe shuttle, yarn brakes (not shown) are used to ensure that theresulting detour at the yarn tensioning device 13 is formed mainly bypulling back the entire inserted weft yarn; where necessary, a length ofyarn is also drawn off from the bobbin 11.

After the return movement of the shuttle and weft yarn, the weft yarn iscut off at the picking end by shears (not shown).

The projecting weft yarn ends on each side of the shed are then tuckedinto the next shed by a selvedge forming mechanism (not shown) after thereed beat up and shedding. The fabric is then would on the cloth beam 3.

The optical weft stop motion includes a transmitter or light source 21which is mounted in a casing 20 secured to the catching mechanism 9beneath the picking line, i.e. the path theoretically covered by theshuttle and a photosensitive electric element or photoelectric cell 23which is mounted in a casing 22 secured to the catching mechanism abovethe picking line. The transmitter serves to emit a concentrated beam 24towards the photoelectric cell 23 transversely of the weft. The casing22 further carries a box 25 containing an electric circuit of the weftstop motion.

Referring to FlG. 2, the electrical circuit of the weft stop motionincludes a switching means for stopping the operation of the weavingmachine. This circuit includes the photoelectric cell 23 which isconnected via a resistor 26 to the input of an amplifier 27. Theamplifier 27 is connected to a Schmitt trigger 28 which converts theamplified photoelectric cell voltage signal into a rectangular signal.The Schmitt trigger 28 has two outputs 28a, 28b which carry two voltageshaving a 180 phase shift. Whenever the Schmitt trigger 28 receives avoltage signal from the photoelectric cell 23 when the latter is fullyilluminated, the state of the trigger changes and the phase of thevoltage signals at the outputs change. The output 280 of the Schmitttrigger 28 is connected to an input 29a of a NAND gate 29, while theoutput 28b is connected to an input 30a of a second NAND gate 30. Asecond input 29b of the gate 29 is connected to a time network 31. Theoutputs 29c and 300 of the gates 29, 30 lead to a monostablemultivibrator 32, whose output 32c is connected via amplifier elements(not shown) to the main switch (not shown) of the weaving machine.Another switch 33 is provided in the switching means and is controlledby the weaving machine main shaft 5. The switch 33, which is normallyclosed, enables a second input 30b of the gate 30 to be selectivelyconnected to earth or, via a resistor 34, to a positive voltage.

In operation, in order to monitor the insertion of a weft yarn, as soonas the shuttle reaches the catching mechanism 9, the switch 33 is openedby the weaving machine main shaft 5. Consequently, the input 30b of thegate 30 is connected via resistor 34 to the positive voltage. However,the phase position of the output voltages of the Schmitt trigger 28 issuch that the voltage at output 30a is not sufficient to allow the gate30 to pass a signal together with the voltage at output 30b. if no weftyarn has been inserted by the shuttle, then there is no weft yarn in thepath of the beam of light 24 between the light source 21 and thephotoelectric cell 23. The cell 23 is thus fully illuminated andgenerates a voltage signal which, after amplification in the amplifier27, actuates the Schmitt trigger 28. The phase of the signal at theinput 30a of the gate 30 thus changes so :that it is now sufficient withthe voltage at input 301), to enable the gate 30 to pass a signal to themonostable multivibrator 32. The state of the multivibrator 32 thuschanges and causes the weaving machine to stop by deactivating the mainswitch of the machine. The same processes occur if the weft yarn breaks,such breakage usually occurring just behind the shuttle. The weft yarnthen forms a small loop near the beam of light, such loop bypassing thebeam and acting as if no weft yarn had been inserted.

If a weft yarn has been inserted by the shuttle, as is the case when theweaving machine is operating normally, the yarn will be situated in thepath of the beam of light 24 so that the beam 24 does not reach thephotoelectric cell 23 and the cell 23 does not produce a signal. Thestate of the Schmitt trigger 28 does not change and the phase of thevoltage of the input 300 of the gate 30 does not change. Thus, the gate30 does not pass a signal, the multivibrator 32 does not change over anddoes not initiate any switching operations to stop the weaving machine.The machine then continues to operate and, after being pushed back, theshuttle is ejected from the catching mechanism 9 (FIG. 1) and returnedto the picking mechanism 8 (FIG. 1). The weft yarn is cut off followedby the beat up operation, shedding and tucking of the ends into the nextshed to form the selvedge. Thus, there is reliably no weft yarn nowsituated in the region of the beam of light 24 between the transmitter21 and receiver 23. The optical parts of the weft yarn stop motion areat this time checked for soiling as follows:

Whenever the switch 33 is opened, the time network 31 is also started,receiving a positive voltage via the resistor 34. The transit time, e.g.120 milliseconds (msec.), of the time network 31 is longer than theopening time of the switch 33, which closes after the insertion of theweft yarn has been monitored. That is, the transit time, which dependson the speed of operation of the weaving machine, is so long that theabove-mentioned time for the optical parts to be checked is reached. Atthis time, the time network 31 delivers a voltage to the input 29b ofthe gate 29. If the optical parts are so dirty that the intensity of thebeam 24 of light reaching the photoelectric cell 23 is inadequate todeliver a voltage signal of sufficient amplitude, the Schmitt trigger 28remains in the position in which the voltage at the output 28a of thetrigger 28 and at the input 29a of the gate 29 is sufficient, togetherwith the voltage at the input 29b, to cause the gate 29 to pass a signalto the multivibrator 32. The state of the multivibrator 32 then changesand thus causes the weaving machine to stop as above. Instead ofallowing the optical parts to become so dirty that the weaving machinemust be stopped, the multivibrator 32 can of course emit a warningsignal when there is slight soiling, so that steps can be taken to cleanthe optical parts.

If the optical parts are sufficiently clean at this time, thephotoelectric cell 23 passes a signal to the Schmitt trigger 28, thestate of which then changes over. The voltage at the input 29a of thegate 29 is now insufficient together with the voltage at the input 2% toopen the gate 29 to deliver a signal so that the multivibrator 32 doesnot change over and the weaving machine continues to operate. Of course,as the switch 33 is closed, the voltage at the gate input 30b isinsufficient with the voltage at the input 30a to cause the gate 30 topass a signal to the multivibrator 32.

The weft yarn stop motion also offers the possibility of monitoringbroken weft yarns which, because they are relatively long, remain in theform of a tangle in the scanning zone. If a weft yarn breaks, the partstill clamped in the shuttle continues to move towards the catchingmechanism 9 and accumulates in the form of a tangle in the region of thebeam of light 24. This tangle is still in the region of the beam oflight24 when the optical parts are checked for dirt. The switching tle, e.its interruption of the beam of light as it passes throug the beam canbe used to form pulses or a pulse can be generated by induction.

I claim:

1. An optical weft stop motion for a weaving machine comprising atransmitter for emitting a beam in the direction of a weft;

and

a receiver for receiving the beam, said receiver including a switchingmeans having an amplifier for receiving a voltage signal from saidreceiver, a Schmitt trigger connected to said amplifier for convertingsaid voltage signal into a rectangular signal, a first NAND gate havinga first input connected to a first output of said Schmitt trigger and asecond input selectively connected to ground or a voltage source, asecond NAND gate having a first input connected to a second output ofsaid Schmitt trigger and a second input selectively connected to groundor the voltage source, a switch for selectively connecting said secondinput of each said NAND gate to ground or the voltage source, a timenetwork connected between said second input of said second NAND gate andsaid switch, a monostable multivibrator connected to an output of eachof said first and second NAND gates for receiving a respective signaltherefrom to deactivate a main switch of the weaving machine in responsethereto.

2. An optical weft stop motion for a weaving machine comprising atransmitter for emitting a beam in the direction of a weft;

and

a receiver for receiving the beam, said receiver including a switchingmeans having a first means for checking for the presence of a weft inthe path of the beam during a weft insertion operation, and a secondmeans for checking the beam intensity of the beam from said transmitterto determine the degree of soiling of said receiver or the presence of atangled weft after a weft insertion operation and for stopping theoperation of the weaving machine in response to said receiver receivinga beam from said transmitter of an intensity less than a predeten'ninedvalue in the absence of a weft in the path of the beam after a weftinsertion operation.

3. An optical system as set forth in claim 2 wherein said switchingmeans is actuated upon movement of a shuttle through the path of thebeam.

4. An optical system as set forth in claim 2 wherein said receiverincludes a photoelectric cell to receive said beam and said switchingmeans includes means for determining the intensity of light received onsaid cell in the absence of a weft in the path of the beam whereby asignal is emitted to stop the operation of the weaving machine inresponse to the intensity oflight being less than said predeterminedvalue.

5. An optical weft stop motion for a weaving machine comprising atransmitter for emitting a beam oflight,

a photocell for receiving the beam, and

a switching means connected to said photocell for selectively stoppingthe operation of the weaving machine in response to said photocellreceiving full illumination from the beam during a picking operation andless than a predetermined value of intensity from the beam aftercompletion of a picking operation.

1. An optical weft stop motion for a weaving machine comprising atransmitter for emitting a beam in the direction of a weft; and areceiver for receiving the beam, said receiver including a switchingmeans having an amplifier for receiving a voltage signal from saidreceiver, a Schmitt trigger connected to said amplifier for convertingsaid voltage signal into a rectangular signal, a first NAND gate havinga first input connected to a first output of said Schmitt trigger and asecond input selectively connected to ground or a voltage source, asecond NAND gate having a first input connected to a second output ofsaid Schmitt trigger and a second input selectively connected to groundor the voltage source, a switch for selectively connecting said secondinput of each said NAND gate to ground or the voltage source, a timenetwork connected between said second input of said second NAND gate andsaid switch, a monostable multivibrator connected to an output of eachof said first and second NAND gates for receiving a respective signaltherefrom to deactivate a main switch of the weaving machine in responsethereto.
 2. An optical weft stop motion for a weaving machine comprisinga transmitter for emitting a beam in the direction of a weft; and areceiver for receiving the beam, said receiver including a switchingmeans having a first means for checking for the presence of a weft inthe path of the beam during a weft insertion operation, and a secondmeans for checking the beam intensity of the beam from said transmitterto determine the degree of soiling of said receiver or the presence of atangled weft after a weft insertion operation and for stopping theoperation of the weaving machine in response to said receiver rEceivinga beam from said transmitter of an intensity less than a predeterminedvalue in the absence of a weft in the path of the beam after a weftinsertion operation.
 3. An optical system as set forth in claim 2wherein said switching means is actuated upon movement of a shuttlethrough the path of the beam.
 4. An optical system as set forth in claim2 wherein said receiver includes a photoelectric cell to receive saidbeam and said switching means includes means for determining theintensity of light received on said cell in the absence of a weft in thepath of the beam whereby a signal is emitted to stop the operation ofthe weaving machine in response to the intensity of light being lessthan said predetermined value.
 5. An optical weft stop motion for aweaving machine comprising a transmitter for emitting a beam of light, aphotocell for receiving the beam, and a switching means connected tosaid photocell for selectively stopping the operation of the weavingmachine in response to said photocell receiving full illumination fromthe beam during a picking operation and less than a predetermined valueof intensity from the beam after completion of a picking operation.